drivers/usb/gadget/function/u_audio.c

   1 /*
   2  * u_audio.c -- interface to USB gadget "ALSA sound card" utilities
   3  *
   4  * Copyright (C) 2016
   5  * Author: Ruslan Bilovol <ruslan.bilovol@gmail.com>
   6  *
   7  * Sound card implementation was cut-and-pasted with changes
   8  * from f_uac2.c and has:
   9  *    Copyright (C) 2011
  10  *    Yadwinder Singh (yadi.brar01@gmail.com)
  11  *    Jaswinder Singh (jaswinder.singh@linaro.org)
  12  *
  13  * This program is free software; you can redistribute it and/or modify
  14  * it under the terms of the GNU General Public License as published by
  15  * the Free Software Foundation; either version 2 of the License, or
  16  * (at your option) any later version.
  17  *
  18  * This program is distributed in the hope that it will be useful,
  19  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21  * GNU General Public License for more details.
  22  */
  23
  24 #include <linux/module.h>
  25 #include <sound/core.h>
  26 #include <sound/pcm.h>
  27 #include <sound/pcm_params.h>
  28
  29 #include "u_audio.h"
  30
  31 #define BUFF_SIZE_MAX   (PAGE_SIZE * 16)
  32 #define PRD_SIZE_MAX    PAGE_SIZE
  33 #define MIN_PERIODS     4
  34
  35 struct uac_req {
  36         struct uac_rtd_params *pp; /* parent param */
  37         struct usb_request *req;
  38 };
  39
  40 /* Runtime data params for one stream */
  41 struct uac_rtd_params {
  42         struct snd_uac_chip *uac; /* parent chip */
  43         bool ep_enabled; /* if the ep is enabled */
  44
  45         struct snd_pcm_substream *ss;
  46
  47         /* Ring buffer */
  48         ssize_t hw_ptr;
  49
  50         void *rbuf;
  51
  52         unsigned max_psize;     /* MaxPacketSize of endpoint */
  53         struct uac_req *ureq;
  54
  55         spinlock_t lock;
  56 };
  57
  58 struct snd_uac_chip {
  59         struct g_audio *audio_dev;
  60
  61         struct uac_rtd_params p_prm;
  62         struct uac_rtd_params c_prm;
  63
  64         struct snd_card *card;
  65         struct snd_pcm *pcm;
  66
  67         /* timekeeping for the playback endpoint */
  68         unsigned int p_interval;
  69         unsigned int p_residue;
  70
  71         /* pre-calculated values for playback iso completion */
  72         unsigned int p_pktsize;
  73         unsigned int p_pktsize_residue;
  74         unsigned int p_framesize;
  75 };
  76
  77 static const struct snd_pcm_hardware uac_pcm_hardware = {
  78         .info = SNDRV_PCM_INFO_INTERLEAVED | SNDRV_PCM_INFO_BLOCK_TRANSFER
  79                  | SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_MMAP_VALID
  80                  | SNDRV_PCM_INFO_PAUSE | SNDRV_PCM_INFO_RESUME,
  81         .rates = SNDRV_PCM_RATE_CONTINUOUS,
  82         .periods_max = BUFF_SIZE_MAX / PRD_SIZE_MAX,
  83         .buffer_bytes_max = BUFF_SIZE_MAX,
  84         .period_bytes_max = PRD_SIZE_MAX,
  85         .periods_min = MIN_PERIODS,
  86 };
  87
  88 static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)
  89 {
  90         unsigned pending;
  91         unsigned long flags, flags2;
  92         unsigned int hw_ptr;
  93         int status = req->status;
  94         struct uac_req *ur = req->context;
  95         struct snd_pcm_substream *substream;
  96         struct snd_pcm_runtime *runtime;
  97         struct uac_rtd_params *prm = ur->pp;
  98         struct snd_uac_chip *uac = prm->uac;
  99
 100         /* i/f shutting down */
 101         if (!prm->ep_enabled) {
 102                 usb_ep_free_request(ep, req);
 103                 return;
 104         }
 105
 106         if (req->status == -ESHUTDOWN)
 107                 return;
 108
 109         /*
 110          * We can't really do much about bad xfers.
 111          * Afterall, the ISOCH xfers could fail legitimately.
 112          */
 113         if (status)
 114                 pr_debug("%s: iso_complete status(%d) %d/%d\n",
 115                         __func__, status, req->actual, req->length);
 116
 117         substream = prm->ss;
 118
 119         /* Do nothing if ALSA isn't active */
 120         if (!substream)
 121                 goto exit;
 122
 123         snd_pcm_stream_lock_irqsave(substream, flags2);
 124
 125         runtime = substream->runtime;
 126         if (!runtime || !snd_pcm_running(substream)) {
 127                 snd_pcm_stream_unlock_irqrestore(substream, flags2);
 128                 goto exit;
 129         }
 130
 131         spin_lock_irqsave(&prm->lock, flags);
 132
 133         if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
 134                 /*
 135                  * For each IN packet, take the quotient of the current data
 136                  * rate and the endpoint's interval as the base packet size.
 137                  * If there is a residue from this division, add it to the
 138                  * residue accumulator.
 139                  */
 140                 req->length = uac->p_pktsize;
 141                 uac->p_residue += uac->p_pktsize_residue;
 142
 143                 /*
 144                  * Whenever there are more bytes in the accumulator than we
 145                  * need to add one more sample frame, increase this packet's
 146                  * size and decrease the accumulator.
 147                  */
 148                 if (uac->p_residue / uac->p_interval >= uac->p_framesize) {
 149                         req->length += uac->p_framesize;
 150                         uac->p_residue -= uac->p_framesize *
 151                                            uac->p_interval;
 152                 }
 153
 154                 req->actual = req->length;
 155         }
 156
 157         hw_ptr = prm->hw_ptr;
 158
 159         spin_unlock_irqrestore(&prm->lock, flags);
 160
 161         /* Pack USB load in ALSA ring buffer */
 162         pending = runtime->dma_bytes - hw_ptr;
 163
 164         if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
 165                 if (unlikely(pending < req->actual)) {
 166                         memcpy(req->buf, runtime->dma_area + hw_ptr, pending);
 167                         memcpy(req->buf + pending, runtime->dma_area,
 168                                req->actual - pending);
 169                 } else {
 170                         memcpy(req->buf, runtime->dma_area + hw_ptr,
 171                                req->actual);
 172                 }
 173         } else {
 174                 if (unlikely(pending < req->actual)) {
 175                         memcpy(runtime->dma_area + hw_ptr, req->buf, pending);
 176                         memcpy(runtime->dma_area, req->buf + pending,
 177                                req->actual - pending);
 178                 } else {
 179                         memcpy(runtime->dma_area + hw_ptr, req->buf,
 180                                req->actual);
 181                 }
 182         }
 183
 184         spin_lock_irqsave(&prm->lock, flags);
 185         /* update hw_ptr after data is copied to memory */
 186         prm->hw_ptr = (hw_ptr + req->actual) % runtime->dma_bytes;
 187         hw_ptr = prm->hw_ptr;
 188         spin_unlock_irqrestore(&prm->lock, flags);
 189         snd_pcm_stream_unlock_irqrestore(substream, flags2);
 190
 191         if ((hw_ptr % snd_pcm_lib_period_bytes(substream)) < req->actual)
 192                 snd_pcm_period_elapsed(substream);
 193
 194 exit:
 195         if (usb_ep_queue(ep, req, GFP_ATOMIC))
 196                 dev_err(uac->card->dev, "%d Error!\n", __LINE__);
 197 }
 198
 199 static int uac_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
 200 {
 201         struct snd_uac_chip *uac = snd_pcm_substream_chip(substream);
 202         struct uac_rtd_params *prm;
 203         struct g_audio *audio_dev;
 204         struct uac_params *params;
 205         unsigned long flags;
 206         int err = 0;
 207
 208         audio_dev = uac->audio_dev;
 209         params = &audio_dev->params;
 210
 211         if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
 212                 prm = &uac->p_prm;
 213         else
 214                 prm = &uac->c_prm;
 215
 216         spin_lock_irqsave(&prm->lock, flags);
 217
 218         /* Reset */
 219         prm->hw_ptr = 0;
 220
 221         switch (cmd) {
 222         case SNDRV_PCM_TRIGGER_START:
 223         case SNDRV_PCM_TRIGGER_RESUME:
 224                 prm->ss = substream;
 225                 break;
 226         case SNDRV_PCM_TRIGGER_STOP:
 227         case SNDRV_PCM_TRIGGER_SUSPEND:
 228                 prm->ss = NULL;
 229                 break;
 230         default:
 231                 err = -EINVAL;
 232         }
 233
 234         spin_unlock_irqrestore(&prm->lock, flags);
 235
 236         /* Clear buffer after Play stops */
 237         if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK && !prm->ss)
 238                 memset(prm->rbuf, 0, prm->max_psize * params->req_number);
 239
 240         return err;
 241 }
 242
 243 static snd_pcm_uframes_t uac_pcm_pointer(struct snd_pcm_substream *substream)
 244 {
 245         struct snd_uac_chip *uac = snd_pcm_substream_chip(substream);
 246         struct uac_rtd_params *prm;
 247
 248         if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
 249                 prm = &uac->p_prm;
 250         else
 251                 prm = &uac->c_prm;
 252
 253         return bytes_to_frames(substream->runtime, prm->hw_ptr);
 254 }
 255
 256 static int uac_pcm_hw_params(struct snd_pcm_substream *substream,
 257                                struct snd_pcm_hw_params *hw_params)
 258 {
 259         return snd_pcm_lib_malloc_pages(substream,
 260                                         params_buffer_bytes(hw_params));
 261 }
 262
 263 static int uac_pcm_hw_free(struct snd_pcm_substream *substream)
 264 {
 265         return snd_pcm_lib_free_pages(substream);
 266 }
 267
 268 static int uac_pcm_open(struct snd_pcm_substream *substream)
 269 {
 270         struct snd_uac_chip *uac = snd_pcm_substream_chip(substream);
 271         struct snd_pcm_runtime *runtime = substream->runtime;
 272         struct g_audio *audio_dev;
 273         struct uac_params *params;
 274         int p_ssize, c_ssize;
 275         int p_srate, c_srate;
 276         int p_chmask, c_chmask;
 277
 278         audio_dev = uac->audio_dev;
 279         params = &audio_dev->params;
 280         p_ssize = params->p_ssize;
 281         c_ssize = params->c_ssize;
 282         p_srate = params->p_srate;
 283         c_srate = params->c_srate;
 284         p_chmask = params->p_chmask;
 285         c_chmask = params->c_chmask;
 286         uac->p_residue = 0;
 287
 288         runtime->hw = uac_pcm_hardware;
 289
 290         if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
 291                 spin_lock_init(&uac->p_prm.lock);
 292                 runtime->hw.rate_min = p_srate;
 293                 switch (p_ssize) {
 294                 case 3:
 295                         runtime->hw.formats = SNDRV_PCM_FMTBIT_S24_3LE;
 296                         break;
 297                 case 4:
 298                         runtime->hw.formats = SNDRV_PCM_FMTBIT_S32_LE;
 299                         break;
 300                 default:
 301                         runtime->hw.formats = SNDRV_PCM_FMTBIT_S16_LE;
 302                         break;
 303                 }
 304                 runtime->hw.channels_min = num_channels(p_chmask);
 305                 runtime->hw.period_bytes_min = 2 * uac->p_prm.max_psize
 306                                                 / runtime->hw.periods_min;
 307         } else {
 308                 spin_lock_init(&uac->c_prm.lock);
 309                 runtime->hw.rate_min = c_srate;
 310                 switch (c_ssize) {
 311                 case 3:
 312                         runtime->hw.formats = SNDRV_PCM_FMTBIT_S24_3LE;
 313                         break;
 314                 case 4:
 315                         runtime->hw.formats = SNDRV_PCM_FMTBIT_S32_LE;
 316                         break;
 317                 default:
 318                         runtime->hw.formats = SNDRV_PCM_FMTBIT_S16_LE;
 319                         break;
 320                 }
 321                 runtime->hw.channels_min = num_channels(c_chmask);
 322                 runtime->hw.period_bytes_min = 2 * uac->c_prm.max_psize
 323                                                 / runtime->hw.periods_min;
 324         }
 325
 326         runtime->hw.rate_max = runtime->hw.rate_min;
 327         runtime->hw.channels_max = runtime->hw.channels_min;
 328
 329         snd_pcm_hw_constraint_integer(runtime, SNDRV_PCM_HW_PARAM_PERIODS);
 330
 331         return 0;
 332 }
 333
 334 /* ALSA cries without these function pointers */
 335 static int uac_pcm_null(struct snd_pcm_substream *substream)
 336 {
 337         return 0;
 338 }
 339
 340 static const struct snd_pcm_ops uac_pcm_ops = {
 341         .open = uac_pcm_open,
 342         .close = uac_pcm_null,
 343         .ioctl = snd_pcm_lib_ioctl,
 344         .hw_params = uac_pcm_hw_params,
 345         .hw_free = uac_pcm_hw_free,
 346         .trigger = uac_pcm_trigger,
 347         .pointer = uac_pcm_pointer,
 348         .prepare = uac_pcm_null,
 349 };
 350
 351 static inline void free_ep(struct uac_rtd_params *prm, struct usb_ep *ep)
 352 {
 353         struct snd_uac_chip *uac = prm->uac;
 354         struct g_audio *audio_dev;
 355         struct uac_params *params;
 356         int i;
 357
 358         if (!prm->ep_enabled)
 359                 return;
 360
 361         audio_dev = uac->audio_dev;
 362         params = &audio_dev->params;
 363
 364         for (i = 0; i < params->req_number; i++) {
 365                 if (prm->ureq[i].req) {
 366                         if (usb_ep_dequeue(ep, prm->ureq[i].req))
 367                                 usb_ep_free_request(ep, prm->ureq[i].req);
 368                         /*
 369                          * If usb_ep_dequeue() cannot successfully dequeue the
 370                          * request, the request will be freed by the completion
 371                          * callback.
 372                          */
 373
 374                         prm->ureq[i].req = NULL;
 375                 }
 376         }
 377
 378         prm->ep_enabled = false;
 379
 380         if (usb_ep_disable(ep))
 381                 dev_err(uac->card->dev, "%s:%d Error!\n", __func__, __LINE__);
 382 }
 383
 384 int u_audio_start_capture(struct g_audio *audio_dev)
 385 {
 386         struct snd_uac_chip *uac = audio_dev->uac;
 387         struct usb_gadget *gadget = audio_dev->gadget;
 388         struct device *dev = &gadget->dev;
 389         struct usb_request *req;
 390         struct usb_ep *ep;
 391         struct uac_rtd_params *prm;
 392         struct uac_params *params = &audio_dev->params;
 393         int req_len, i;
 394
 395         ep = audio_dev->out_ep;
 396         prm = &uac->c_prm;
 397         config_ep_by_speed(gadget, &audio_dev->func, ep);
 398         req_len = prm->max_psize;
 399
 400         prm->ep_enabled = true;
 401         usb_ep_enable(ep);
 402
 403         for (i = 0; i < params->req_number; i++) {
 404                 if (!prm->ureq[i].req) {
 405                         req = usb_ep_alloc_request(ep, GFP_ATOMIC);
 406                         if (req == NULL)
 407                                 return -ENOMEM;
 408
 409                         prm->ureq[i].req = req;
 410                         prm->ureq[i].pp = prm;
 411
 412                         req->zero = 0;
 413                         req->context = &prm->ureq[i];
 414                         req->length = req_len;
 415                         req->complete = u_audio_iso_complete;
 416                         req->buf = prm->rbuf + i * prm->max_psize;
 417                 }
 418
 419                 if (usb_ep_queue(ep, prm->ureq[i].req, GFP_ATOMIC))
 420                         dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
 421         }
 422
 423         return 0;
 424 }
 425 EXPORT_SYMBOL_GPL(u_audio_start_capture);
 426
 427 void u_audio_stop_capture(struct g_audio *audio_dev)
 428 {
 429         struct snd_uac_chip *uac = audio_dev->uac;
 430
 431         free_ep(&uac->c_prm, audio_dev->out_ep);
 432 }
 433 EXPORT_SYMBOL_GPL(u_audio_stop_capture);
 434
 435 int u_audio_start_playback(struct g_audio *audio_dev)
 436 {
 437         struct snd_uac_chip *uac = audio_dev->uac;
 438         struct usb_gadget *gadget = audio_dev->gadget;
 439         struct device *dev = &gadget->dev;
 440         struct usb_request *req;
 441         struct usb_ep *ep;
 442         struct uac_rtd_params *prm;
 443         struct uac_params *params = &audio_dev->params;
 444         unsigned int factor, rate;
 445         const struct usb_endpoint_descriptor *ep_desc;
 446         int req_len, i;
 447
 448         ep = audio_dev->in_ep;
 449         prm = &uac->p_prm;
 450         config_ep_by_speed(gadget, &audio_dev->func, ep);
 451
 452         ep_desc = ep->desc;
 453
 454         /* pre-calculate the playback endpoint's interval */
 455         if (gadget->speed == USB_SPEED_FULL)
 456                 factor = 1000;
 457         else
 458                 factor = 8000;
 459
 460         /* pre-compute some values for iso_complete() */
 461         uac->p_framesize = params->p_ssize *
 462                             num_channels(params->p_chmask);
 463         rate = params->p_srate * uac->p_framesize;
 464         uac->p_interval = factor / (1 << (ep_desc->bInterval - 1));
 465         uac->p_pktsize = min_t(unsigned int, rate / uac->p_interval,
 466                                 prm->max_psize);
 467
 468         if (uac->p_pktsize < prm->max_psize)
 469                 uac->p_pktsize_residue = rate % uac->p_interval;
 470         else
 471                 uac->p_pktsize_residue = 0;
 472
 473         req_len = uac->p_pktsize;
 474         uac->p_residue = 0;
 475
 476         prm->ep_enabled = true;
 477         usb_ep_enable(ep);
 478
 479         for (i = 0; i < params->req_number; i++) {
 480                 if (!prm->ureq[i].req) {
 481                         req = usb_ep_alloc_request(ep, GFP_ATOMIC);
 482                         if (req == NULL)
 483                                 return -ENOMEM;
 484
 485                         prm->ureq[i].req = req;
 486                         prm->ureq[i].pp = prm;
 487
 488                         req->zero = 0;
 489                         req->context = &prm->ureq[i];
 490                         req->length = req_len;
 491                         req->complete = u_audio_iso_complete;
 492                         req->buf = prm->rbuf + i * prm->max_psize;
 493                 }
 494
 495                 if (usb_ep_queue(ep, prm->ureq[i].req, GFP_ATOMIC))
 496                         dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
 497         }
 498
 499         return 0;
 500 }
 501 EXPORT_SYMBOL_GPL(u_audio_start_playback);
 502
 503 void u_audio_stop_playback(struct g_audio *audio_dev)
 504 {
 505         struct snd_uac_chip *uac = audio_dev->uac;
 506
 507         free_ep(&uac->p_prm, audio_dev->in_ep);
 508 }
 509 EXPORT_SYMBOL_GPL(u_audio_stop_playback);
 510
 511 int g_audio_setup(struct g_audio *g_audio, const char *pcm_name,
 512                                         const char *card_name)
 513 {
 514         struct snd_uac_chip *uac;
 515         struct snd_card *card;
 516         struct snd_pcm *pcm;
 517         struct uac_params *params;
 518         int p_chmask, c_chmask;
 519         int err;
 520
 521         if (!g_audio)
 522                 return -EINVAL;
 523
 524         uac = kzalloc(sizeof(*uac), GFP_KERNEL);
 525         if (!uac)
 526                 return -ENOMEM;
 527         g_audio->uac = uac;
 528         uac->audio_dev = g_audio;
 529
 530         params = &g_audio->params;
 531         p_chmask = params->p_chmask;
 532         c_chmask = params->c_chmask;
 533
 534         if (c_chmask) {
 535                 struct uac_rtd_params *prm = &uac->c_prm;
 536
 537                 uac->c_prm.uac = uac;
 538                 prm->max_psize = g_audio->out_ep_maxpsize;
 539
 540                 prm->ureq = kcalloc(params->req_number, sizeof(struct uac_req),
 541                                 GFP_KERNEL);
 542                 if (!prm->ureq) {
 543                         err = -ENOMEM;
 544                         goto fail;
 545                 }
 546
 547                 prm->rbuf = kcalloc(params->req_number, prm->max_psize,
 548                                 GFP_KERNEL);
 549                 if (!prm->rbuf) {
 550                         prm->max_psize = 0;
 551                         err = -ENOMEM;
 552                         goto fail;
 553                 }
 554         }
 555
 556         if (p_chmask) {
 557                 struct uac_rtd_params *prm = &uac->p_prm;
 558
 559                 uac->p_prm.uac = uac;
 560                 prm->max_psize = g_audio->in_ep_maxpsize;
 561
 562                 prm->ureq = kcalloc(params->req_number, sizeof(struct uac_req),
 563                                 GFP_KERNEL);
 564                 if (!prm->ureq) {
 565                         err = -ENOMEM;
 566                         goto fail;
 567                 }
 568
 569                 prm->rbuf = kcalloc(params->req_number, prm->max_psize,
 570                                 GFP_KERNEL);
 571                 if (!prm->rbuf) {
 572                         prm->max_psize = 0;
 573                         err = -ENOMEM;
 574                         goto fail;
 575                 }
 576         }
 577
 578         /* Choose any slot, with no id */
 579         err = snd_card_new(&g_audio->gadget->dev,
 580                         -1, NULL, THIS_MODULE, 0, &card);
 581         if (err < 0)
 582                 goto fail;
 583
 584         uac->card = card;
 585
 586         /*
 587          * Create first PCM device
 588          * Create a substream only for non-zero channel streams
 589          */
 590         err = snd_pcm_new(uac->card, pcm_name, 0,
 591                                p_chmask ? 1 : 0, c_chmask ? 1 : 0, &pcm);
 592         if (err < 0)
 593                 goto snd_fail;
 594
 595         strlcpy(pcm->name, pcm_name, sizeof(pcm->name));
 596         pcm->private_data = uac;
 597         uac->pcm = pcm;
 598
 599         snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &uac_pcm_ops);
 600         snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, &uac_pcm_ops);
 601
 602         strlcpy(card->driver, card_name, sizeof(card->driver));
 603         strlcpy(card->shortname, card_name, sizeof(card->shortname));
 604         sprintf(card->longname, "%s %i", card_name, card->dev->id);
 605
 606         snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_CONTINUOUS,
 607                 snd_dma_continuous_data(GFP_KERNEL), 0, BUFF_SIZE_MAX);
 608
 609         err = snd_card_register(card);
 610
 611         if (!err)
 612                 return 0;
 613
 614 snd_fail:
 615         snd_card_free(card);
 616 fail:
 617         kfree(uac->p_prm.ureq);
 618         kfree(uac->c_prm.ureq);
 619         kfree(uac->p_prm.rbuf);
 620         kfree(uac->c_prm.rbuf);
 621         kfree(uac);
 622
 623         return err;
 624 }
 625 EXPORT_SYMBOL_GPL(g_audio_setup);
 626
 627 void g_audio_cleanup(struct g_audio *g_audio)
 628 {
 629         struct snd_uac_chip *uac;
 630         struct snd_card *card;
 631
 632         if (!g_audio || !g_audio->uac)
 633                 return;
 634
 635         uac = g_audio->uac;
 636         card = uac->card;
 637         if (card)
 638                 snd_card_free(card);
 639
 640         kfree(uac->p_prm.ureq);
 641         kfree(uac->c_prm.ureq);
 642         kfree(uac->p_prm.rbuf);
 643         kfree(uac->c_prm.rbuf);
 644         kfree(uac);
 645 }
 646 EXPORT_SYMBOL_GPL(g_audio_cleanup);
 647
 648 MODULE_LICENSE("GPL");
 649 MODULE_DESCRIPTION("USB gadget \"ALSA sound card\" utilities");
 650 MODULE_AUTHOR("Ruslan Bilovol");